Back to EveryPatent.com
United States Patent |
5,231,119
|
Govoni
,   et al.
|
July 27, 1993
|
Crystalline olefin polymers and copolymers in the form of spherical
particles at high porosity
Abstract
Crystalline olefin polymers and copolymers in the form of spherical
particles having porosity (expressed in percentage of voids) higher than
15%, with more than 90% of the pores having a pore diameter greater than
one micron. These polymeric particulate materials find many applications,
including, e.g., the preparation of masterbatches containing significant
quantities of additives and/or pigments.
Inventors:
|
Govoni; Gabriele (Ferrara, IT);
Ciarrocchi; Antonio (Ferrara, IT);
Sacchetti; Mario (Ferrara, IT)
|
Assignee:
|
Himont Incorporated (Wilmington, DE)
|
Appl. No.:
|
718680 |
Filed:
|
June 21, 1991 |
Current U.S. Class: |
523/221; 521/56; 521/134; 521/143; 521/144; 526/125.6; 526/347.2; 526/351; 526/352 |
Intern'l Class: |
C08F 002/00; C08F 004/42; C08J 009/28 |
Field of Search: |
523/221
526/347.2,352,351,124
521/143,144
|
References Cited
U.S. Patent Documents
3450682 | Jun., 1969 | Sasaki et al. | 526/347.
|
3953414 | Apr., 1976 | Galli et al. | 526/352.
|
4293673 | Oct., 1981 | Hamer et al. | 526/352.
|
4380507 | Apr., 1983 | Noristi et al. | 526/352.
|
4983693 | Jan., 1991 | Haag et al. | 526/124.
|
Foreign Patent Documents |
290149 | Sep., 1988 | EP.
| |
Primary Examiner: Michl; Paul R.
Assistant Examiner: Asinovsky; Olga
Parent Case Text
RELATED APPLICATIONS
This application is a continuation-in-part of our application Ser. No.
07/515,300 filed Apr. 27, 1990, abandoned and of our application Ser. No.
07/515,390 entitled "COMPONENTS AND CATALYSTS FOR THE POLYMERIZATION OF
OLEFINS" filed Apr. 27, 1990, abandoned, the contents of each being
incorporated hereby by reference.
Claims
We claim:
1. Crystalline homopolymers of an olefin of the formula CH.sub.2 .dbd.CHR,
wherein R is hydrogen, an alkyl radical having 2 to 6 carbon atoms, or
aryl, and crystalline copolymers of said olefin with another different
olefin of said formula or with propylene, wherein the amount of propylene
in said copolymers is less than 30% by weight, said polymers and
copolymers being in the form of spherical particles with an average
diameter between 50 and 5000 microns and a porosity expressed in void
percentage greater than 15%.
2. The spherical particles of claim 1, wherein more than 40% of the pores
have a diameter greater than one micron.
3. The spherical particles of claim 1, and wherein more than 90% of the
pores have a diameter greater than one micron.
4. The spherical particles of claim 1, wherein the void percentage is
between 20 and 40%.
5. The spherical particles of claim 1 containing additives, fillers and/or
pigments in an amount greater than 10% by weight.
Description
FIELD OF THE INVENTION
This invention relates to crystalline olefin polymers and copolymers in the
form of spherical particles with an average diameter between 50 and 7000
microns and porosity and surface area characteristics which make them
suitable for, e.g., the preparation of masterbatches containing
significant quantities of pigment and/or additives.
BACKGROUND OF THE INVENTION
It is known that catalyst components for the polymerization of olefins
comprising a titanium compound supported on a magnesium halide in active
form can be obtained in spherical particle form suitable for the
development of polymers with optimum morphological characteristics.
Components of this type are described in U.S. Pat. Nos. 3,953,414 and
4,399,054. Specifically, the polymers obtained with the catalysts of U.S.
Pat. No. 4,399,054 are in spherical particle form having high flowability
and high bulk density.
The porosity (around 10% expressed in percentage of voids) and the surface
area, however, are not sufficiently high to allow their use, particularly
in the field of masterbatch preparation when said masterbatch contain a
significant quantity of pigments and/or additives.
SUMMARY OF THE INVENTION
Now it has been found that it is possible to obtain crystalline olefin
homopolymers and copolymers in spherical particle form having various
advantages by polymerization of olefins of the formula CH.sub.2 .dbd.CHR
wherein R is hydrogen, an alkyl radical with 2-6 carbon atoms or is aryl
such as phenyl or substituted phenyl. The foregoing olefin may be
homopolymerized or may be copolymerized with another different olefin of
the foregoing formula, or may be copolymerized with propylene, wherein the
amount of propylene in the resulting copolymer is less than 30% by weight.
The crystalline olefin polymer or copolymer is in spherical particle form
with an average diameter between 50 and 5000 microns, a porosity expressed
in percentage of voids which is greater than 15% and preferably is between
15% and 40%, and wherein more than 40% of the pores have a diameter
greater than one micron.
The spherical form particles exhibit a lowered degree of crystallinity
relative to a polymer of equivalent crystallizability which has undergone
melt pelletization. Reduced crystallinity coupled with the highly porous
nature of the sphere provides particular benefits when the material is
used as a substrate for subsequent reactions.
Typical spherical polymeric materials show the following properties:
percent porosity=15-35%;
particle size distribution=100% of the spherical particles have a diameter
between 1000 and 3000 microns; preferably 40-50% of the particles have a
diameter between 1000 and 2000 microns, and 35-45% between 2000 and 3000
microns;
more than 90% of the pores have a diameter greater than one micron.
The percent porosity is determined by absorption of mercury according to
the method described hereinafter.
DETAILED DESCRIPTION
The catalysts used in the preparation of the foregoing spherical polymers
and copolymers are obtained from catalyst components having particular
morphological properties, including a titanium halide or titanium
haloalcoholate, supported on magnesium chloride.
The spherical catalyst components are obtained from adducts of magnesium
chloride with alcohols generally containing 3 moles of alcohol per mole of
MgCl.sub.2, prepared by emulsifying, in the molten state, the adduct in an
inert hydrocarbon liquid immiscible with the melted adduct, then cooling
the emulsion in a very short time in order to effect solidification of the
adduct in the form of spherical particles.
The particles are then subjected to partial dealcoholization using a
heating cycle at a temperature increasing from 50.degree. to 130.degree.
C. until the alcohol content is reduced from 3 to a value as low as 0.1,
preferably from 0.1 to 1.5 moles per mole of MgCl.sub.2.
The adducts thus obtained are suspended cold in TiCl.sub.4, at a
concentration of 40-50 g/1, and then brought to a temperature of
80.degree.-135.degree. C. where they are maintained for 1-2 hours.
An electron-donor compound can also be added to the TiCl.sub.4 selected,
preferably, from the alkyl, cycloaklyl or aryl esters of phthalic acid,
such as diisobutyl, di-n-butyl and di-n-octyl phthalate.
The excess TiCl.sub.4 is then removed hot through filtration or
sedimentation, and the treatment with TiCl.sub.4 is repeated one or more
times. The solid is then washed with heptane or hexane and then dried.
The catalyst components obtained in this manner have the following
properties:
surface area=less than 100 m.sup.2 /g, preferably less than 80 m.sup.2 /g;
porosity (nitrogen)=0.20-0.50 ml/g;
pore volume distribution such that more than 50% of the pores have a radius
greater than 100 .ANG..
The catalyst is obtained by mixing the solid catalyst component with an
Al-trialkyl compound, preferably Al-triethyl or Al-triisobutyl.
The Al/Ti ratio is generally between 10 and 800.
The polymerization of ethylene and/or the other olefins is carried out
according to known techniques operating in liquid phase or in the gas
phase. The polymerization temperature is preferably between 70.degree. and
90.degree. C. The catalysts can be precontacted with small quantities of
olefin (prepolymerization), maintaining the catalyst in suspension in a
hydrocarbon solvent, polymerizing at a temperature between room
temperature and 60.degree. C., and producing quantities of polymer greater
than 0.5 times the weight of the catalyst component.
The prepolymerization can also be carried out in liquid propylene, in which
case quantities of polymer up to 1000 times the weight of the catalyst can
be produced.
The resulting spherical polymer particles may be used in the preparation of
masterbatches according to known techniques. One such technique involves
permitting the polymer to absorb a solution or emulsion of the additive
filler or pigment in a solvent, and then evaporating the solvent. The
quantity of additive which remains incorporated depends on the
concentration of the solution or emulsion itself. Another technique
involves effecting the absorption of the additive or mixtures of additives
in the melted form.
If the substances which constitute the additive, fillers, or pigments are
solid and have a high melting point, said substances can be added in
powder form to the polymer particles using paraffin oils or liquid wetting
and surface-active agents such as liquid ethoxylated amines in order to
obtain a good adhesion. It is preferable to use powders with a particle
size lower than 10 .mu.m.
In any case, masterbatches can be prepared very simply by feeding the
polymer particles and at least one additive, pigment, filler or
combinations thereof, in normal mixers for powders, and mixing for the
desired residence time.
The preferred mixers are those having a velocity from about 150 rpm (for
mixers with an internal volume of about 130 liters), up to 500 rpm (for
mixers with a smaller internal volume of up to about 10 liters) which are
thermoregulated. The use of thermoregulated mixers is particularly
recommended.
The mixers are equipped with spray-feeders for the liquids, and
hopper-feeders for the solids. The substances which can be fed in the
molten state are normally melted in autoclaves under nitrogen.
When operating according to the above-mentioned methods one can obtain
concentrations of additives, pigments, or fillers, or combinations
thereof, up to 20%-30% by weight with respect to the total weight of the
concentrate. Obviously these maximum values are not absolute, since when
operating, for instance, with fillers having a high specific gravity, one
can reach concentrations around 50% by weight. The minimum concentration
value is a function of the additives, fillers, or pigments which are used,
and of the concentration which one wants to obtain in the final products.
In some cases it is possible to go down to a concentration of 5% by weight
with respect to the total weight of the concentrate.
The additives pigments and/or fillers that can be used are those normally
added to polymers in order to impart desired properties. They include
stabilizers, fillers, nucleating agents, slip agents, lubricant and
antistatic agents, flame retardants, plasticizers, and blowing agents.
A large number of different grades of olefin polymers can be obtained in
the form of spherical particles according to the invention. The polymers
include high density polyethylenes (HDPE: density greater than 0.940),
comprising homopolymers of ethylene and copolymers of ethylene with
alpha-olefins having from 3 to 12 carbon atoms; linear low-density
polyethylenes (LLDPE: density less than 0.940); very low and ultra low
density linear polyethylenes (VLLDPE and ULLDPE; density less than 0.920
and as low as 0.890), said LLDPE, VLLDPE and ULLDPE consisting of
copolymers of ethylene and one or more alpha-olefins having from 3 to 12
carbon atoms, with a content of units derived from ethylene of over 80% by
weight; crystalline polymers and copolymers of butene-1,
4-methyl-pentene-1, and styrene.
The data reported in the following examples are determined as indicated
below:
______________________________________
Property Method
______________________________________
MIL flowability index
ASTM-D 1238
Surface area B.E.T. (apparatus used
SORPTOMATIC 1800-C. Erba)
Porosity (nitrogen)
B.E.T. (see above)
Bulk density DIN-53194
Flowability The time needed for 100 g of
polymer to flow through a
funnel with an outlet hole of
1.27 cm in diameter and the
walls of which are inclined
at 20.degree. C. to the vertical
Morphology ASTM-D 1921-63
______________________________________
The porosity expressed as percentage of voids is determined through
absorption of mercury under pressure. The volume of mercury absorbed
corresponds to the volume of the pores. In order to determine this, a
dilatometer is used with calibrated probe (3 mm diam.) C D3 (C. Erba)
connected to a mercury reservoir and a high vacuum rotating pump
(1.times.10.sup.-2 mba).
A weighted quantity of the sample (about 0.5 g) is introduced into the
dilatometer. The apparatus is then brought to a high vacuum (<0.1 mm Hg)
and held for 10 minutes. The dilatometer is then connected to the mercury
reservoir and the mercury is allowed to flow in slowly until it reaches
the level marked on the probe at a height of 10 cm.
The valve that connects the dilatometer to the vacuum pump is closed and
the apparatus is pressurized with nitrogen (2.5 kg/cm.sup.2) The pressure
causes the mercury to penetrate the pores and the level lowers in
accordance with the porosity of the material. After the measure on the
probe where the new mercury level has stabilized is determined, the volume
of the pores is calculated as follows: V=R.sup.2 .pi..multidot..DELTA.H
where R is the radius of the probe in cm, and .DELTA.H is the difference
in level in cm between the initial and final levels of the mercury column.
By weighing the dilatometer, dilatometer+mercury and
dilatometer+mercury+sample, a value of apparent sample volume prior to
pore penetration can be calculated. The volume of the sample is given by:
##EQU1##
wherein P is the weight of the sample in g;
Pl is the weight in g of the dilatometer+mercury;
P2 is the weight in g of the dilatometer+mercury+sample;
D is the density of the mercury (at 25.degree. C.=13.546 g/cc)
The porosity percentage is given by:
##EQU2##
The following examples further illustrate the invention.
EXAMPLE 1
A MgCl.sub.2.3C.sub.2 H.sub.5 OH adduct in spherical particle form, which
particles have a diameter from 30 to 150 microns, is prepared following
the method described in Example 2 of U.S. Pat. No. 4,399,054, the
disclosures of said method being incorporated herein by reference,
operating at 5,000 rpm instead of 10,000 rpm. The resultant adduct is then
dealcoholated by heating with temperature increasing from 50.degree. to
100.degree. C. under a nitrogen stream until the alcohol content reaches
1.2 mole for each mole MgCl.sub.2. The adduct thus obtained has a surface
area of 11.5 m.sup.2 /g.
31.2 g of said adduct are added in a reaction vessel under agitation at
0.degree. C. to 625 ml of TiCl.sub.4. Then the foregoing mixture is heated
to 100.degree. C. for one hour. When the temperature reaches 40.degree.
C., diisobutyl phthalate s added in a molar ratio Mg/diisobutyl
phthalate=8. The contents of the vessel are then heated to 100.degree. C.
for 1 hour, left to settle and subsequently the liquid is syphoned off
hot. 500 ml of TiCl.sub.4 are added, the solid and the contents of the
vessel heated to 120.degree. C. for one hour, the reaction mixture is then
left to settle and the liquid is syphoned off hot. The resulting solid is
washed 6 times with 200 ml aliquots of anhydrous hexane at 60.degree. C.
and then 3 times at room temperature. The solid catalyst component, after
drying under vacuum, has the following characteristics:
Ti content=2.5% by weight;
porosity (nitrogen)=0.261 cc/g;
surface area=66.4 m.sup.2 /g.
Using 0.02 g of this solid, an ethylene polymerization is conducted in a
2.5 1 stainless steel autoclave equipped with an agitator and a
thermostatic system, which had been degassed with nitrogen at 70.degree.
C. for one hour.
At 45.degree. C. there is introduced in H.sub.2 stream 900 ml of a solution
containing 0.5 g/1 of Al-triisobutyl in anhydrous hexane and immediately
afterwards, the catalyst component is suspended in 100 ml of the
above-mentioned solution.
The temperature is rapidly brought to 75.degree. C. and H.sub.2 is fed
until the pressure reaches 3 atm, then ethylene is fed up to 10.5 atm.
These conditions are maintained for 3 hours, replenishing continuously the
ethylene depleted. At the end of the polymerization reaction, the
autoclave is rapidly vented and cooled at room temperature.
The polymeric suspension is filtered and the solid residue dried in
nitrogen at 60.degree. C. for 8 hours.
400 g of polyethylene are obtained with the following characteristics:
MIE=0.25 g/10';
MIF=7.8 g/10';
MIF/MIE=31.2;
morphology=100% spherical particles with diameter between 1000 and 5000
.mu.m;
flowability=12 sec.;
bulk density=0.38 g/cc;
void percentage=30.
EXAMPLE 2
By partially dealcoholating (as per Example 1) a MgCl.sub.2.3EtOH spherical
adduct obtained according to the method indicated in the preceding
example, an adduct is obtained with ETOH/MgCl.sub.2 molar ratio of 0.15
with the following characteristics:
porosity (mercury)=1.613 cc/g;
surface area=22.2 m.sup.2 /g.
By treatment of the foregoing adduct with TiCl.sub.4 at a temperature of
135.degree. C. (concentration=50 g/1) for one hour three successive times,
a spherical catalyst component is obtained which, after elimination of
excess TiCl.sub.4 by washing with n-hexane and subsequent drying, exhibits
the following characteristics:
Ti=2% by wt.;
porosity (nitrogen)=0.435 cc/g;
surface area=44.0 m.sup.2 /g.
Using 0.012 of this component in the polymerization of ethylene as
described in Example 1, 380 g of polyethylene are obtained with the
following characteristics:
MIE=0.205 g/10';
MIF=16.42 g/10';
MIF/MIE=80.1;
flowability=12 sec.;
bulk density=0.40 g/cc;
void percentage=23.5%;
morphology=100% spherical particles with diameter between 1000-5000.mu..
EXAMPLE 3
20 kg of polyethylene in spherical particle form obtained with a continuous
ethylene polymerization test using a catalyst obtained from solid catalyst
component and co-catalyst components of Example 1 are introduced into a
Loediga FM 130 P mixer lined with steam at 100.degree. C. and mixed for 5
minutes at a blade speed of 150 rpm until the temperature of the polymer
reaches 70.degree. C. 5 kg of Atmer 163 product (Atlas) are then sprayed
into the mixer at 100.degree. C. The agitation is continued for 15 minutes
and then the product is discharged. The polymer thus obtained is in the
form of spherical particles with 100% of the particles having a diameter
from 1000 to 5000 microns which particles contain 19.8% by weight of Atmer
product and have a flowability of 13 sec.
Variations can of course be made without departing from the spirit of our
invention as set out in the following claims.
Top